Composite organic-inorganic nanoparticles (COINs) with chemically encoded optical signatures

To obtain a coding system for multiplex detection, we have developed a method to synthesize a new type of nanomaterial called composite organic-inorganic nanoparticles (COINs). The method allows the incorporation of a broad range of organic compounds into COINs to produce surface enhanced Raman scattering (SERS)-like spectra that are richer in variety than fluorescence-based signatures. Preliminary data suggest that COINs can be used as Raman tags for multiplex and ultrasensitive detection of biomolecules.     

Ultrasensitive Detection of Prostate‐Specific Antigen and Thrombin Based on Gold‐Upconversion Nanoparticle Assembled Pyramids

Self‐assembled nanostructures have been used for the detection of numerous cancer biomarkers. In this study, a gold‐upconversion‐nanoparticle (Au‐UCNP) pyramid based on aptamers is fabricated to simultaneously detect thrombin and prostate‐specific antigen (PSA) using surface‐enhanced Raman scattering (SERS) and fluorescence, respectively. The higher the concentration of thrombin, the lower the intensity of SERS. PSA connected with the PSA aptamer leads to an increase in fluorescence intensity. The limit of detection of thrombin and PSA reaches 57 × 10^?18 and 0.032 × 10^?18m , respectively. In addition, the pyramid also exhibits great target specificity. The results of human serum target detection demonstrate that the Au‐UCNP pyramid is an excellent choice for the quantitative determination of cancer biomarkers, and is feasible for the early diagnosis of cancer.     

Preparation of highly stable oligo(ethylene glycol) derivatives-functionalized gold nanoparticles and their application in LSPR-based detection of PSA/ACT complex

A sandwich immunoassay for PSA/ACT complex detection based on gold nanoparticle aggregation using two probes was developed. The functionalized colloidal gold nanoparticles (AuNPs) showed highly stable not only in the presence of high ionic strength but also in a wide pH range. The functionalized AuNPs were tagged with PSA/ACT complex monoclonal antibody and goat PSA polyclonal antibody and served as the probes to induce aggregation of the colloidal particles. As a result, PSA/ACT complex was detected at concentrations as low as 1 ng/ml. This is the first time that a new aggregation sandwich-immunoassay technique using two gold probes has been used, and the results are generally applicable to other LSPR-based immunoassays.     

Reverse-phase versus sandwich antibody microarray, technical comparison from a clinical perspective

Protein microarrays are powerful tools to quantify and characterize proteins in multiplex assays. They have great potential within clinical diagnostics and prognostics, as they minimize consumption of both analyte and biological sample. Assays that do not require labeling of the biological specimen, henceforth called label-free, are vital for ease of clinical sample processing. Here, we evaluate two label-free techniques, reverse-phase and sandwich antibody assays, using microarrays on high-performance porous silicon surfaces and fluorescence detection. In view of increasing interest in reverse microarrays, this paper focuses on analytical sensitivity of the reverse assays compared to the more complex but highly sensitive sandwich assay. Sensitivity, linear range, and reproducibility of the two assays were compared using prostate-specific antigen (PSA) in buffer. The sandwich assay displayed 5 orders of magnitude lower detection limit (0.7 ng/mL) compared to the reverse assay (70 microg/mL). PSA at 50 nM (1.5 microg/mL) in cell lysates was detected by the sandwich assay but not by the reverse assay, demonstrating again a far lower detection limit for sandwich microarrays. In independent assay runs of PSA spiked in female serum, the sandwich assay had good linearity (R2 > 0.99) and reproducibility (coefficient of variation < or =15%), and the detection limit could be improved to 0.14 ng/mL. Without further signal amplification, the sandwich assay would be our choice for PSA analysis of clinical samples using a microarray technology platform.     

Coherent-array imaging using phased subarrays. Part I: basic principles

The front-end hardware complexity of a coherent array imaging system scales with the number of active array elements that are simultaneously used for transmission or reception of signals. Different imaging methods use different numbers of active channels and data collection strategies. Conventional full phased array (FPA) imaging produces the best image quality using all elements for both transmission and reception, and it has high front-end hardware complexity. In contrast, classical synthetic aperture (CSA) imaging only transmits on and receives from a single element at a time, minimizing the hardware complexity but achieving poor image quality. We propose a new coherent array imaging method--phased subarray (PSA) imaging--that performs partial transmit and receive beam-forming using a subset of adjacent elements at each firing step. This method reduces the number of active channels to the number of subarray elements; these channels are multiplexed across the full array and a reduced number of beams are acquired from each subarray. The low-resolution subarray images are laterally upsampled, interpolated, weighted, and coherently summed to form the final high-resolution PSA image. The PSA imaging reduces the complexity of the front-end hardware while achieving image quality approaching that of FPA imaging.     

乙炔基芳酰胺酸硅烷改进石英纤维/含硅芳炔复合材料高温界面性能

运用自主设计合成的含有端炔和芳酰胺酸结构的硅烷偶联剂(CA-K)改善石英纤维(QF)/含硅芳炔(PSA)复合材料的高温界面黏结性能。FTIR、DSC以及TGA跟踪分析表明:CA-K在PSA固化时同步发生热闭环, 形成耐热的酰亚胺环结构, CA-K同时参与PSA的固化;XPS分析推断出CA-K与纤维发生化学键合;CA-K处理后QF/PSA复合材料的界面黏结强度增加, 常温下层间剪切强度(ILSS)和弯曲强度分别较未处理时提高了34.7%和40.4%, 在250 ℃时ILSS和弯曲强度的保留率分别达到82.5%和54.9%, 而500 ℃时ILSS和弯曲强度保留率为85.1%和64.2%。      

Carbon nanotube microwell array for sensitive electrochemiluminescent detection of cancer biomarker proteins

This paper describes fabrication of a novel electrochemiluminescence (ECL) immunosensor array featuring capture-antibody-decorated single-wall carbon nanotube (SWCNT) forests residing in the bottoms of 10-μL wells with hydrophobic polymer walls. Silica nanoparticles containing [Ru(bpy)(3)](2+) and secondary antibodies (RuBPY-silica-Ab(2)) are employed in this system for highly sensitive two-analyte detection. Antibodies to prostate specific antigen (PSA) and interleukin-6 (IL-6) were attached to the same RuBPY-silica-Ab(2) particle. The array was fabricated by forming the wells on a conductive pyrolytic graphite chip (1 in. × 1 in.) with a single connection to a potentiostat to achieve ECL. The sandwich immunoassay protocol employs antibodies attached to SWCNTs in the wells to capture analyte proteins. Then RuBPY-silica-Ab(2) is added to bind to the captured proteins. ECL is initiated in the microwells by electrochemical oxidation of tripropyl amine (TprA), which generates excited state [Ru(bpy)(3)](2+) in the 100-nm particles, and is measured with a charge-coupled device (CCD) camera. Separation of the analytical spots by the hydrophobic wall barriers enabled simultaneous immunoassays for two proteins in a single sample without cross-contamination. The detection limit (DL) for PSA was 1 pg mL(-1) and for IL-6 was 0.25 pg mL(-1) (IL-6) in serum. Array determinations of PSA and IL-6 in patient serum were well-correlated with single-protein ELISAs. These microwell SWCNT immunoarrays provide a simple, sensitive approach to the detection of two or more proteins.     

Detection of Receptor-Ligand Interactions With an GHz Impedance Biosensor System

Nanogap impedance biosensors with an electrode separation of 75 nm have been used for the specific detection of biological interactions. Different model systems, such as thrombin-anti-thrombin antibody, and Rev-peptide-anti-Rev aptamer are presented to demonstrate the detectability of different molecular masses at varying concentrations. In order to improve the signal-to-noise ratio, the use of reference sensors has been explored. The interaction of prostate specific antigen (PSA) with an anti-PSA antibody is shown to demonstrate the detection at concentrations as low as 10 nM.     

PSA接枝碳纳米管增强PVA/PSA共混物薄膜的微结构与性能

通过溶液浇铸及化学交联,制备了聚(苯乙烯磺酸钠-co-丙烯酸)接枝碳纳米管(PSA-g-MWNT)增强聚乙烯醇(PVA)/PSA复合膜,着重研究了改性碳纳米管对复合膜的微观结构、力学性能、电导率、离子交换容量(IEC)和吸水率的影响。结果表明,当PVA与PSA质量比为2∶1时,PVA/PSA共混物薄膜的综合性能最佳。接枝在MWNT表面的PSA提高了MWNT与PVA/PSA共混物之间的相容性,实现了MWNT对PVA/PSA薄膜的同时增强、增韧。随着PSA-g-MWNT含量的增加,PVA/PSA/PSA-g-MWNT复合膜的电导率显著提高,IEC值也呈升高的趋势。     

Immunoassay readout method using extrinsic Raman labels adsorbed on immunogold colloids

An immunoassay readout method based on surface-enhanced Raman scattering (SERS) is described. The method exploits the SERS-derived signal from reporter molecules that are coimmobilized with biospecific species on gold colloids. This concept is demonstrated in a dualanalyte sandwich assay, in which two different antibodies covalently bound to a solid substrate specifically capture two different antigens from an aqueous sample. The captured antigens in turn bind selectively to their corresponding detection antibodies. The detection antibodies are conjugated with gold colloids that are labeled with different Raman reporter molecules, which serve as extrinsic labels for each type of antibody. The presence of a specific antigen is established by the characteristic SERS spectrum of the reporter molecule. A near-infrared diode laser was used to excite efficiently the SERS signal while minimizing fluorescence interference. We show that, by using different labels with little spectral overlap, two different antigenic species can be detected simultaneously. The potential of this concept to function as a readout strategy for multiple analytes is briefly discussed.     

Development of highly fluorescent detection reagents for the construction of ultrasensitive immunoassays

We developed two kinds of highly fluorescent streptavidin-based conjugates for use as universal detection reagents in ultrasensitive immunoassays. The direct conjugate was produced by covalently linking streptavidin to poly(Glu: Lys) which was labeled heavily with Eu chelates; the indirect conjugate was made by first conjugating bovine serum albumin (BSA) to poly(Glu:Lys) labeled heavily with Eu chelates and then further linking streptavidin to the conjugate of BSA-poly(Glu:Lys)-Eu chelate. Both direct and indirect conjugates were used to construct a highly sensitive time-resolved fluorometric assay for prostate-specific antigen (PSA). Of two monoclonal antibodies used in the assay, one was coated on the well surface of the microtitration strips, and the other was biotinylated. When 10 microL of sample volume was used, we found that the assay using the indirect conjugate had a detection limit of 0.006 microg/L, which was approximately 5.6-fold more sensitive than the one using Eu chelate directly labeled detection antibody and 6.8-fold more sensitive than the one using Eu chelate-labeled streptavidin. However, the assay that used the direct conjugate was 1.5-fold more sensitive than the one that utilized the indirect conjugate. When 45 microL of sample volume was used, a detection limit of 0.001 microg/L was achieved by using the direct conjugate. This improvement in sensitivity should be equally obtainable for the analytes other than PSA. We further demonstrated that the final immunoassay performance was affected not only by the quality of the streptavidin-based conjugate used but also by the quality of the biotinylated antibody reagent. The universal detection reagents described here are believed to be particularly useful for the construction of ultrasensitive time-resolved fluorometric immunoassays and are potentially applicable in other fields such as immunohistochemistry and nucleic acid detection.     

基于改进的线性判别分析识别重叠并发的双故障

在两维空间中,当关键质量特性之间存在相关关系并且预定义故障类之间重叠时,传统的模糊聚类算法FCM对双故障并发的识别率会下降。为了提升对重叠并发双故障的识别率,一种新算法PILDA被提出,该算法提出的主成分修整能够消除重叠的影响,而双故障判别区间确定的方法则能够实现对未预定义的并发双故障的识别。经过864种不同相关关系和均值偏移量的故障组合仿真实验,结果表明PILDA能有效识别并发故障及预定义单发故障,平均识别率为84.94%,明显高于FCM的58.13%。该方法具有一定的应用价值。     

Discrimination of breast cancer by measuring prostate-specific antigen levels in women's serum

Prostate-specific antigen (PSA) has been reported to be a potential biomarker of breast cancer. Serum PSA of normal women is around 1 pg/mL, which is usually undetectable by current assay methods; thus an ultrasensitive measurement of PSA expression in women's serum is necessary to distinguish normal from malignant breast diseases. To enhance the sensitivity of conventional immunoassay technology for the detection of PSA in sera, we adopted a localized surface plasmon coupled fluorescence fiber-optic biosensor, which combines a sandwich immunoassay with the localized surface plasmon technique. The concentration of total PSA (t-PSA) (from 0.1 to 1000 pg/mL) in phosphate-buffered saline solution and the normalized fluorescence signal exhibit a linear relationship where the correlation coefficient is 0.9574. In addition, the concentration of additional t-PSA in 10-fold-diluted healthly women's serum across a similar range was measured. The correlation coefficient for this measurement is 0.9142. In clinical serum samples, moreover, the experimental results of t-PSA detection show that both the mean value and median of normalized fluorescence signals in the breast cancer group (155.2 and 145.7, respectively) are higher than those in the noncancer group (46.6 and 37.1, respectively). We also examined the receiver operating characteristic curve for t-PSA, and the area under the curve (AUC) is estimated to be 0.9063, the AUC being used to measure the performance of a test to correctly identify diseased and nondiseased subjects.     

清洗工艺对变压吸附制氧的影响

通过一套小型两塔变压吸附制氧实验装置,研究了小流量连续清洗与大流量瞬间清洗两种不同清洗工艺对变压吸附制氧性能的影响。实验结果表明,在保持产氧量相同的情况下,分别采用两种清洗工艺均可大幅提高产氧浓度,得到最高约91%的产品氧气浓度,产氧浓度对大流量瞬间清洗时间的变化更为敏感;而同时采用两种清洗工艺时,最高产氧浓度可达93%以上。     

Amplified electrochemical detection of a cancer biomarker by enhanced precipitation using horseradish peroxidase attached on carbon nanotubes

An electrochemical nanoimmunosensor based on multiwall carbon nanotubes (MWCNTs)/gold nanoparticles (AuNPs) was developed for the amplified detection of prostate specific antigen (PSA). The amplified detection was achieved by the enhanced precipitation of 4-chloro-1-naphthol (CN) using a higher number of horseradish peroxidase (HRP) molecules attached on MWCNTs. The PSA nanoimmunosensor was fabricated by immobilizing a monoclonal anti-PSA antibody (anti-PSA) on the AuNP-attached thiolated MWCNT on a gold electrode. The sensor surface was characterized using scanning electron microscope, transmission electron microscope, quartz crystal microbalance, and electrochemical techniques. Cyclic and square wave voltammetric techniques were used to monitor the enhanced precipitation of CN that accumulated on the electrode surface and subsequent decrement in the electrode surface area by monitoring the reduction process of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple. Under the optimized experimental condition, the linear range and the detection limit of PSA immunosensor were determined to be 1.0 pg/mL to 10.0 ng/mL and 0.40 ± 0.03 pg/mL, respectively. The validity of the proposed method was compared with an enzyme-linked immunosorbent assay method in various PSA spiked human serum samples.     

Simultaneous and continuous multiple wavelength absorption spectroscopy on nanoliter volumes based on frequency-division multiplexing fiber-loop cavity ring-down spectroscopy

We demonstrate a method for measuring optical loss simultaneously at multiple wavelengths with cavity ring-down spectroscopy (CRD). Phase-shift CRD spectroscopy is used to obtain the absorption of a sample from the phase lag of intensity modulated light that is entering and exiting an optical cavity. We performed dual-wavelength detection by using two different laser light sources and frequency-division multiplexing. Each wavelength is modulated at a separate frequency, and a broadband detector records the total signal. This signal is then demodulated by lock-in amplifiers at the corresponding two frequencies allowing us to obtain the phase-shift and therefore the optical loss at several wavelengths simultaneously without the use of a dispersive element. In applying this method to fiber-loop cavity ring-down spectroscopy, we achieve detection at low micromolar concentrations in a 100 nL liquid volume. Measurements at two wavelengths (405 and 810 nm) were performed simultaneously on two dyes each absorbing at mainly one of the wavelengths. The respective concentrations could be quantified independently in pure samples as well as in mixtures. No crosstalk between the two channels was observed, and a minimal detectable absorbance of 0.02 cm(-1) was achieved at 405 nm.     

SERS-encoded nanocomposites for dual pathogen bioassay

Surface-enhanced Raman spectroscopy(SERS) has been successfully applied to detect various biomolecules, but it is still in challenge to assay living cells or bacteria sensitively, selectively and quantitatively in complex environments. In this paper, 4-ATP and DTNB are assembled on Ag nanoparticle(NP)-decorated poly(styrene-co-acrylic acid)(PSA) nanospheres and then sealed by silica shells to form sensitive SERS labels based on the localized surface plasmon resonance of Ag NPs and large light scattering cross-sections of PSA nanospheres. They are further developed as encoding tags for dual detection of S. aureus and E. coli after assembling corresponding aptamers, which demonstrate ultralow detection limits of 8 cell L-1 for S. aureus and 2 cell L-1 for E. coli. Such a bioassay indicates a point-of-care strategy of ultrasensitively biomedical detections by encoding specific SERS tags.     

On-line fault detection and diagnosis obtained by implementingneural algorithms on a digital signal processor

A measurement instrument for on-line fault detection and diagnosis is proposed. It is based on the implementation of a neural network algorithm on a processor specialized in digital signal processing and provided with suitable data acquisition and generation units. Two specific implementations are detailed. The former uses the neural-network to simulate on-line the correct system behavior, thus allowing the fault detection to be achieved by comparing the neural network output with the measured one. The latter uses the neural network to classify on-line the system as correct or faulty, thus allowing the fault detection and diagnosis to be achieved simultaneously. These two implementations are applied to detect on-line and diagnose faults on a real system in order to point out different fields of application and to highlight the performance of the measurement apparatus     

On Restoring Interference in Joint Photon Counting Rate in Cascade Emission

Abstract

We propose an experimental scheme utilizing the different travelling speed of photons at different frequencies to ‘erase’ the time sequential distinguishability of photons emitted from the two steps of an atomic cascade. Interference in joint detection requires not only the overlapping of the same photon in time through different paths, but also the presence of both photons simultaneously.     

Femtomolar detection of prostate-specific antigen: an immunoassay based on surface-enhanced Raman scattering and immunogold labels

A novel reagent for low-level detection in immunoadsorbent assays is described. The reagent consists of gold nanoparticles modified to integrate bioselective species (e.g., antibodies) with molecular labels for the generation of intense, biolyte-selective surface-enhanced Raman scattering (SERS) responses in immunoassays and other bioanalytical applications. The reagent is constructed by coating gold nanoparticles (30 nm) with a monolayer of an intrinsically strong Raman scatterer. These monolayer-level labels are bifunctional by design and contain disulfides for chemisorption to the nanoparticle surface and succinimides for coupling to the bioselective species. There are two important elements in this label design; it both minimizes the separation between label and particle surface and maximizes the number of labels on each particle. This approach to labeling also exploits several other advantages of SERS-based labels: narrow spectral bandwidth, resistance to photobleaching and quenching, and long-wavelength excitation of multiple labels with a single excitation source. The strengths of this strategy are demonstrated in the detection of free prostate-specific antigen (PSA) using a sandwich assay format based on monoclonal antibodies. Detection limits of approximately 1 pg/mL in human serum and approximately 4 pg/mL in bovine serum albumin have been achieved with a spectrometer readout time of 60 s. The extension of the method to multianalyte assays (e.g., the simultaneous determination of the many complexed forms of PSA) is discussed.